I am in need of a 63" Ujoint to Ujoint driveshaft. From what I've read that means it needs to be at least 3.5" diameter. I am willing to buy a u-weld-it kit or a custom drive shaft or a junkyard part. I do prefer to save money, so I prefer the junkyard or home remedy. Where are people getting custom drive shafts for their projects? I would love to go to a junkyard in just measure a bunch of cars, but I do not live anywhere near a nice junkyard. Also, what is it like to weld your own and have it balanced? I would likely pay somebody who actually welds to weld it up for me, and then have it balanced at a shop.
You need a straight shaft with no slip joint, or does need to include a slip joint?
I've got a slip joint in my transmission so I'm just looking for a straight shaft.
I have shortened one myself. Had it balanced by a shop and they were impressed by how close it was - there was skepticism as to whether it would be useable.
How exact is the 63" measurement?
Its time consuming, but you can probably search rock auto to check length and figure out what has a 63" driveshaft.
I took a look and you can get close at 62" or 63.75" with a 2003 F150, but I'm sure there are many more option that might get you close enough if you have some tolerance on the 63"
No Time said:
How exact is the 63" measurement?
I pushed my slip yoke in until it bottomed out and pulled it out ~½" to get that 63" measurement. I think that's right?
I built the last one I needed because it was an odd setup with CV joints on both ends instead of U-Joints. The local driveshaft shop just looked at me cross-eyed when I talked to them about it.
It has about 40 race hours on it and seems to be holding up very well. Spicer has a pretty good calculator for figuring the diameter based on critical speed. https://spicerparts.com/calculators/critical-speed-rpm-calculator
In reply to Toyman! :
Thanks for the link... I didn't even know that was something to worry about!
I seem to remember something as "the" aluminum driveshaft junkyard donor - Crown Vic maybe? Would likely need shortening.
Keith Tanner said:
I have shortened one myself. Had it balanced by a shop and they were impressed by how close it was - there was skepticism as to whether it would be useable.
I've made a number of them, never balanced any, and never had any problems. I mean, how out of balance can a 3" diameter piece of tubing be?
How far does a slip yoke have to be into the transmission? This is an IRS car so it won't change. If I can pull it out an inch and get a 62" shaft, then I've found exactly what I want/need
In reply to Toyman! :
That calculator doesn't like my numbers, but I'm finding driveshafts for sale that also have very low critical speeds according to that calculator.
In reply to buzzboy :
I like 3/4" for irs cars. Just gives a little more room to get it into position without sacrificing spline engagement at the trans.
Familiar with a race car that threw a balance weight on a driveshaft. On the back straight at Road Atlanta he radioed in that he thought something was falling apart.
Fortunately we have a good driveshaft building/balancing shop nearby. Kevin's Machine in Crawfordville Florida. 1200 hp mud bog trucks are hard on drivelines, just saying.
In reply to buzzboy :
Are you using driveshaft RPMs or engine RPMs? Driveshaft RPM will need to be figured out based on tire circumference and expected top speed.
The Solstice driveshaft I started with was 2". The Spicer calculator stated 3-1/2". I figure the OEMs have a lot more engineering brainpower than I do and Spicer is probably conservative with their numbers. I went with the Spicer numbers and that gave me a shaft good to 140 mph which is faster than the car will ever go.
I found this bad boy that is the right length and right Ujoint type and seems like a reasonable price. Reviews for this brand are all over the place
https://southwestspeed.com/products/700-0000
Toyman! said:
In reply to buzzboy :
Are you using driveshaft RPMs or engine RPMs? Driveshaft RPM will need to be figured out based on tire circumference and expected top speed.
Redline in 4th is about 100mph and 5000rpms so 5000rpm shaft speed as well. The Spicer calculator said 3900 is critical speed.
MadScientistMatt said:
I seem to remember something as "the" aluminum driveshaft junkyard donor - Crown Vic maybe? Would likely need shortening.
They're a little short for my application 😬 My S-klasse is a big girl
Did not read but
Buy a driveshaft(s) with the ends you need and have it made to length at a driveshaft shop.
Did this with many frankenstien Jeeps.
Easy.
In reply to preach :
My closest driveshaft shop is like 3 hours away, so I'm trying to make that a lesser option.
Also there's this, but I don't know how it's measured. Some are end to end and some Ujoint to Ujoint and it doesn't list what type of Ujoints it uses.
https://www.rockauto.com/en/moreinfo.php?pk=13686369&cc=1050927&pt=2308&jsn=1402
A good driveshaft builder will tell you how to measure. Pay me now, or pay me later... 
buzzboy said:
In reply to preach :
My closest driveshaft shop is like 3 hours away, so I'm trying to make that a lesser option.
Also there's this, but I don't know how it's measured. Some are end to end and some Ujoint to Ujoint and it doesn't list what type of Ujoints it uses.
https://www.rockauto.com/en/moreinfo.php?pk=13686369&cc=1050927&pt=2308&jsn=1402
If you look up the application you can then look up the replacement u-joints
Looks like it's for:
Peabody said:
Keith Tanner said:
I have shortened one myself. Had it balanced by a shop and they were impressed by how close it was - there was skepticism as to whether it would be useable.
I've made a number of them, never balanced any, and never had any problems. I mean, how out of balance can a 3" diameter piece of tubing be?
Looking back at my notes, it was my ability to get the u-joints properly aligned that caused the skepticism. Turns out I was within 0.5 degrees, so no problem there.
I guess an inconsistent weld bead thickness could lead to an imbalance? After all, the thing is spinning awfully quickly. Faster than engine speed in an overdrive gear.
Purple Frog said:
A good driveshaft builder will tell you how to measure. Pay me now, or pay me later...
Driveshaft sellers though, like rock auto, list some as total length, some as center to center and some as compressed length.
Following this. Driveshafts have always been something that I have passed on fabricating it my self. Mostly because failure of one and it being so close to me has scared me.
